Which sensor type reads infrared energy to detect occupancy?

Which sensor type reads infrared energy to detect occupancy?

• A. Passive infrared
• B. Active infrared
• C. Ultrasonic
• D. Capacitive

Answer: (A)

A passive infrared sensor reads infrared energy emitted by people in a space to detect occupancy. It uses a pyroelectric detector to sense changes in infrared radiation across its sensing elements. When a warm body moves, different parts of the sensor experience changes in infrared levels, producing a signal the control system interprets as presence. It’s passive because it does not emit energy itself. The other sensor types use different principles: active infrared emits its own beam and looks for interruption or reflection; ultrasonic uses sound waves to detect motion; capacitive sensing relies on changes in an electric field due to nearby objects, not infrared energy.

A passive infrared sensor reads infrared energy emitted by people in a space to detect occupancy. It uses a pyroelectric detector to sense changes in infrared radiation across its sensing elements. When a warm body moves, different parts of the sensor experience changes in infrared levels, producing a signal the control system interprets as presence. It’s passive because it does not emit energy itself. The other sensor types use different principles: active infrared emits its own beam and looks for interruption or reflection; ultrasonic uses sound waves to detect motion; capacitive sensing relies on changes in an electric field due to nearby objects, not infrared energy.